import math   # 导入整个math模块
print(math.pi)  # 输出圆周率π值

from datetime import date     # 只从datetime里取出date类
today = date.today()          # 获取今天的日期
print(today)

# 或者也可以给它取个别名方便书写
import numpy as np  
arr=np.array([1,2,3])